<select name="{$field.name}" id="{$field.name}" class="form-control" {$field.extra_attr|default=''} multiple>
    <option value=''>请选择</option>
    {foreach name="field.options" item="option" key="option_key"}
        {php}if(is_array($option)):{/php}
            <option value="{$option_key}" {present name="field.value"}{eq name="field.value" value="$option_key"} selected{/eq}{/present}
                {foreach name="option" item="option2" key="option_key2"}
                    {$option_key2}="{$option2}"
                {/foreach}>
                {$option.title}
            </option>
        {php}else:{/php}
            <option value="{$option_key}" {present name="field.value"}{eq name="field.value" value="$option_key"} selected{/eq}{/present}>{$option}</option>
        {php}endif;{/php}
    {/foreach}
</select>
